1. Created By: Haley Vrazel
Embryo Transfer
Created By: Haley Vrazel

2. Objectives Analyze in great depth embryo transfer
List and describe the 4 steps of embryo transfer
Compare and Contrast AI with ET
Argue the pros and cons of ET

3. What is Embryo Transfer?
Embryo transfer is the removal of embryos from a super ovulated mare and the transfer of those embryos to less fertile, inferior, older mares

4. History of Embryo Transfer
rabbit embryos were transferred from donor rabbits to surrogate/recipient rabbits
the first bovine (cow) embryo was successfully collected
- popular practice by 1950’s, but surgical method only
1964 – non-surgical method of embryo collection
- used AI tools to perform, procedure based on AI
first successful equine embryo transfer was reported
widely used mid 1980’s

5. Embryo Transfer Facts
Embryo transfer is the most widely used assisted reproductive technique for the mare
80% recovery of fertilized eggs
65% pregnancy rate for transferred embryos

6. Embryo Transfer (ET) Procedure
4 Basic Steps:
Superovulate the Donor Mare
Synchronize the donor and the recipient
Embryo flush
Embryo transfer

7. Step 1 of ET Superovulate Donor Mare Hormone Therapy
Superovulation – The process of releasing many eggs at once
all eggs come from same mare
Hormone Therapy
Progesterone: Maintains pregnancy and prevents the estrus cycle
Prostaglandin: Controls estrous cycle
- same hormones occur naturally in their reproductive system

8. Step 1 Continued Why superovulate?
To produce as many viable eggs as possible
To increase the chances of pregnancy
To utilize all mares so that the maximum number of foals can be produced
Which mares would you superovulate and which ones would you not?
Superovulate the donor – superior quality, younger
Recipient - older, subfertile, undesirable characteristics

9. Step 2 of ET Step 2 – Synchronize Donor and Recipient
Step 2 – Synchronize Donor and Recipient
Photoperiod Manipulation
Short Cycle
- expose to artificial lighting to trick them into estrus
Hormone Therapy
Progesterone
Prostaglandin
hCG: Causes ovulation
- many shots given in combination to initiate onset of estrus
Synchronize 2 recipients per donor
- can’t always guarantee the embryo will take therefore double your chances
Ovulation of recipient and donor must be within 12 hours
recreates same hormonal levels the embryo is used to
Why synchronize the mares?
The donor’s environment should be duplicated
To ensure survival of embryo
*Which one would you synchronize the other to? Why?
Synchronize the recipient to the donor

10. Step 2 Cont. Synchronize 2 recipients per donor
can’t always guarantee the embryo will take therefore double your chances
Ovulation of recipient and donor must be within 12 hours
recreates same hormonal levels the embryo is used to
Why synchronize the mares?
The donor’s environment should be duplicated
To ensure survival of embryo
*Which one would you synchronize the other to? Why? Synchronize the recipient to the donor

11. Thinking Question
Which one would you synchronize the other to? Why? Synchronize the recipient to the donor

12. Step 3 of ET Step 3 – Embryo Flush Embryos graded 1 – 4
Remove embryos by flushing with sterile solution
Flush 7-8 days after insemination
Embryos graded 1 – 4
1:Excellent
2:Good
3:Poor
4:Extremely Poor
*Based on the embryo grades – which ones would you transfer? Why?
Transfer grades 1 and 2 only because they are most viable and will develop healthy offspring
Why wait 7-8 days?
Size and development of embryo

13. Step 4 Step 4 – Transfer of Embryo Similar to AI
Surgically or Non Surgically
Similar to AI
A tube containing the embryo is inserted into the uterus, the embryo is pushed out and will attach to the lining of the uterus
When the recipient delivers the foal, whose genes are being expressed?
Only the donor mare and the stallion. The recipient mare is simply housing the embryo

14. Thinking Questions Compare and contrast AI with embryo transfer.
Compare – both use insemination gun, pressurized system, sterile tools, enter the vagina and empty into the uterine body.
Contrast – ET deals with embryo, AI is simply sperm; ET uses excess fluids; ET uses extra tools and has more methods i.e. surgical/nonsurgical
Which would you prefer as a breeder
surgical or nonsurgical? Why?
- personal choice

15. Resources

16. Objectives Analyze in great depth embryo transfer
List and describe the 4 steps of embryo transfer
Compare and Contrast AI with ET
Argue the pros and cons of ET